Periodic Classifications:-

       

Mendeleev's Periodic Table:-

The present system of classification of elements is based upon the periodic law enunciated by a Russian Chemist Mendeleev. He found that if the element are listed in order of increasing atomic masses (ascending order) certain sets or properties are re-occur periodically. Mendeleev's periodic law is also known as the law of extension of Newland's law of octave. He stated this fact in the form of law in 1869 according to which :
         "The physical and chemical properties of elements are periodic function of their atomic masses.

Mendeleev's Periodic Table:-

In Mendeleev periodic table the element have been arranged in increasing order of their atomic masses in horizontal series in such a way that the elements having similar properties are placed in the same vertical column (groups). Mendeleev periodic table had no zero groups. Mendeleev periodic table is also known as short form periodic table.

Advantanges of Mendeleev's Periodic Table:-

A) Prediction of New Elements:
    There are many vacant spaces or groups in Mendeleev's periodic table.
The Mendeleev predicts the properties of unknwon elements that would occupy these spaces. The prediction was found correct after discoveries of these elements. For example the places for Scandium, Gallium and Germanium were left bank which were discovery later.

B) Correction of Doubtful Atomic Masses:
      Another advantages of using sequence of increasing masses is the correction of some doubtful atomic masses, for example the atomic masses of Beryllium was corrected from 13.5 to 9 with the mass of Beryllium was given the position between the Lithium and Boron.

C) Systematic Study of Elements:-
    Mendeleev's periodic table has helped the chemist to study the properties of elements more systematically. For example, the study of sodium metal helped the chemist to predict the properties of other alkali metals, similarly the study chlorine means to large extent the study of all halogens.

Disadvantages Of Mendeelev's Periodic Law and Periodic Table:-

A) Irregular Position Of Elements:
    When elements are arrange in order or ascending atomic masses Potassium should precede Argon, Nickel should precede Cobalt and Iodine should preced Tellurium but the correct position of elements in the perdioc table is that Argon precede Potassium, Cobalt precede Nickel and Tellurium precede Iodine.

B) Position of Isotopes:
Mendeleev periodic table does not give any position for isotope. If isotopes are placed in ascending order wity respect to atomic masses, the arrangement of other elements are disturb.

C) Position of Lanthanides And Actinides Series:

Lanthanides and Actinides are series of 14 elements each. These series have not been assign any place in the periodic table according to the periodic law.

D) Dissimilar Elements Are Placed In The Same Groups:

Alkali metals ( Lithium, Sodium, potassium, Rubidium and cesium and Francium) metals and coinage metals copper silver and Aurum which are differ widely in properties are placed in the same group. However this discrepancy has been removed later by placing them into two sub-group A family and B Family.

Mosley's Or Modern Periodic Law:-

In 1913 a British Physicist, Mosley found that atomic number is the fundamental properties of an atom instead of atomic mass. He proved beyond doubt that the properties of elements are well explained and most of their anomalies and defect of Mendeleev periodic table disappear if the basis of arrangement of element are changed from mass to atomic number. This formulate the modern periodic law state as:
            "The physical and chemical properties of element are the periodic function of atomic number" when the elements are arranged in the ascending order of their atomic number, the element possising similar properties are repeated at regular interval.

Modern Periodic Table:-

Interbation union of Pure and applied chemistry (IUPAC) recommended modern periodic table in 1984. In this periodic table the elements are arranged in the ascending order of their atomic number instead of their atomic masses, and for furthur development of atomic structure, modern periodic law may be state as:
   " The physical and chemical properties of elements are fuction of their electronic configuration of their atoms which vary with increasing atomic numbers in a periodic manner". Mosley's modern periodic table also known as long form of periodic table.
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Advantages Of Modern Periodic Law/Modern Periodic Table.

1) In modern periodic table the position of an element is releated to electronic configuration of its atom.
2) ‎There is gradual change in properties of element (i.e physical and chemical ) with increase in their atomic numbers.
3) ‎outer transition (d Block) and inner tranistion (f block) elements are aloted a situation between s block and p block.
4) ‎Metals and non-metals are completely separated to each other.
5) ‎The arrangement of atoms is easy to remember and re-produce.
6) ‎The greates advantages of modern periodic table is that this can be divided into four blocks s block p block d block and f block.
7) ‎Modern periodic table solve the problem of misfit pair or elements and position of rare earth elements (i.e lanthanides and actinides series)
8) ‎It has also solve the position of isotopes, since all the isotopes of elements have same atomic number, therefore they need only one place in the periodic table.